As personal electronic devices become increasingly sophisticated, people are using such devices in new and interesting ways. For example, personal or portable electronic devices, such as head-mounted displays (HMD) (e.g., glasses, goggles, or helmets), smart phones, tablets, portable media players, and e-book readers, can be used to “augment reality.” That is, electronic devices can be used as a viewfinder into the real world and virtual elements can be overlaid to create a reality that is enhanced or augmented. Augmented reality can be implemented for applications as varied as visual design, medical care, gaming, navigation, or information retrieval. Conventional augmented reality systems and techniques that use a single camera and/or active vision; however, may not accurately determine the distance to physical objects positioned in the real world. As a result, the virtual elements that are overlaid on the representation of the physical objects may not be displayed at a correct scale. Further, in many conventional systems, error in determining camera height often times results in an error in the determined distance between a real world object and the computing device. This error in the determined distance can affect the scale of virtual elements that are overlaid on the representation of physical objects, which can be distracting, misleading, or even annoying for many users.